1. Field of the Invention
The present invention relates to an apparatus for sensing the feeding of individual sheets of paper, and more particularly, to an apparatus for sensing the feeding of individual sheets of paper in which the feeding of two or more overlapping sheets can be detected in a sheet feeding apparatus for continuously transferring sheets of paper one by one along a predetermined paper traveling path
2. Description of the Related Art
In general, such a sheet feeding apparatus can be adapted for use in combination with, for example, a printing machine in a printing house, an automatic teller machine (ATM) in a bank, and the like. The sheet feeding apparatus is equipped with a driving roller and a driven roller which contact each other, and has a sheet feeding scheme in which a sheet of paper is fed between the driving roller and the driven roller such that they are compressed against the sheet of paper
For example, in the case of a printing machine in a printing house, individual sheets of paper to be printed are transferred from section to section so that different processes are performed in sequences and if the individual sheets of paper are not correctly supplied, there may be a paper jam or printing may be adversely affected. In addition, in the case of an automatic teller machine (ATM), the number of bills of cash and bank notes dispensed by the ATM must be accurately checked.
When a sheet feeding apparatus for transferring individual sheets of paper does not supply sheets of paper one by one but rather feeds two or more sheets of paper at a time, an error occurs in the sheet feeding apparatus during its feeding operation and this can lead to further problems as well. Thus, it is required to always check the thickness of a sheet of paper fed between two corresponding rollers pressed against the sheet of paper.
FIG. 1 is a schematic longitudinal sectional view illustrating the construction of a typical sheet feeding apparatus given as an example to explain a conventional individual paper feed sensing apparatus.
Referring to FIG. 1, the sheet feeding apparatus is provided with a plurality of pairs of driving roller 12 and a driven roller 14 which are supported on a frame 10 The outer surfaces of the driving roller 12 and the driven roller 14 in each pair are in contact with each other to discharge to the outside a sheet of paper P fed therebetween along a predetermined paper traveling path. The driving rollers 12 are mechanically coupled to each other through a power transfer means such as gears, belts or the like, and rotate by means of a separate drive motor (not shown) to feed a sheet of paper along the predetermined paper traveling path such that the driving rollers 12 and the driven rollers 14 are compressed against the sheet of paper.
In the meantime, the sheet feeding apparatus as constructed above includes a paper feed sensing apparatus for detecting the thickness of a sheet of paper being fed. The paper feed sensing apparatus functions to check a space between the driving rollers 12 and the driven rollers 14 which are in contact with each other. There are also diverse kinds of paper feed sensing apparatuses, but almost all paper feed sensing apparatuses employ a paper feed sensing mechanism in which they detect a physical variation in the space between the driving rollers 12 and the driven rollers 14 and then output the detected result to the outside through an electronic sensor 18.
For this purpose, a driving roller 12 and a driven roller 14 coupled to the sensor 18 are replaced by a metal driving roller 20 and a support bearing 22, respectively, which have been machined very precisely. The outer surface of the metal driving roller 20 is treated very precisely and its concentricity is very precise. The support bearing 22 serves as a driven roller whose outer surface is in contact with that of metal driving roller 20. Of course, the support bearing 22 is manufactured such that its outer surface is also treated very precisely to have more precise concentricity.
The metal driving roller 20 and the support bearing 22, machined precisely as mentioned above, are coupled to the sensor 18. Accordingly, when there is a variation in the thickness of a sheet of paper passing between the metal driving roller 20 and the support bearing 22, the distance between the center axes of rotational motion of the metal driving roller 20 and the support bearing 22 are also changed, which is detected by the sensor 18.
However, in the case of such a conventional paper feed sensing apparatus, when the metal driving roller 20 and the support bearing 22 are not manufactured with sufficient precision, the apparatus does not operate reliably. Generally, a sheet of paper has a thickness of 0.1 mm or less. Thus, if either the metal driving roller 20 or the support bearing 22 is slightly eccentric or its outer surface is slightly non-uniform, the thickness of a sheet of paper being fed cannot be detected correctly.
For example, when a sheet of paper having a thickness of 0.1 mm passes between the metal driving roller 20 and the support bearing 22 in a state in which external foreign matter is adhered to the outer surface of either the metal driving roller 20 or the support bearing 22, the sensor 18 detects the total thickness obtained by adding the thickness of the sheet and that of the foreign matter. At this time, if the thickness of the foreign matter is 0.1 mm, the sensor 18 will recognize one sheet of paper as two sheets of paper.
Moreover, the sensor 18 measures the distance between the rotational center axes of the metal driving roller 20 and the support bearing 22 to detect a variation in the distance. Accordingly, if foreign matter adhered to the outer surface of either the metal driving roller 20 or the support bearing 22 has an irregular thickness or pattern, there occurs a variation in the distance between the rotational center axes of the metal driving roller 20 and the support bearing 22, which may make it impossible to measure the distance between the rotational center axes thereof. Further, when the support bearing is constructed as a ball having a number of balls fit into a space between the rotational center axis and the outer surface of a wheel portion, the space between the rotational center axis and the outer surface of the wheel portion is not constant on a microscopic level.
As a result, for the above-mentioned conventional paper feed sensing apparatus, there is the problem in that it must employ a high-priced metal driving roller 20 and support bearing 22 whose outer surface is machined very precisely and whose concentricity is very precise, thereby increasing the manufacturing cost. In addition, there is a limitation of measurement in that when foreign matter is adhered to the outer surface of either the metal driving roller 20 or the support bearing 22, measurement is inaccurate. There arises a further problem in that a separate device for preventing the adhesion of foreign matter is required, thereby increasing both the complexity of the paper feed sensing apparatus and the frequency of malfunction.
To solve the above-described problems, it is a primary object of the present invention to provide an apparatus for sensing the feeding of individual sheets of paper adapted for use with a sheet feeding apparatus, which can simplify the structure of the sheet feeding apparatus, reduce the frequency of malfunction, and enable the feeding of two or more overlapping sheets of paper between driving rollers and driven rollers to always be detected correctly and reliably irrespective of presence of foreign matter on the rollers and without using expensive rollers, bearings or the like as a means for sensing the thickness of a sheet of paper being fed.
To accomplish the primary object of the present invention, there is provided an apparatus for sensing the feeding of individual sheets of paper which is adapted for use with a sheet feeding apparatus including a plurality of pairs of a driving roller and a driven roller which continuously feed a plurality sheets of paper one by one along a predetermined paper traveling path, the apparatus for sensing the feeding of individual sheets of paper comprising a support plate mounted between and adapted to support a sheet of paper passing between the driving roller and driven roller of each of the plurality of pairs of a driving roller and a driven roller along the predetermined paper traveling path, the support plate having a plurality of driving roller through-holes formed thereon which allows the plurality of pairs of a driving roller and a driven roller to contact each other therethough, a rotating shaft rotatably mounted over the top surface of the support plate, parallel to the support plate, an extending contact arm fixedly mounted on the rotating shaft with one end portion thereof extending toward the support plate to contact the top surface of the support plate, the extending contact arm being moved upward from the top surface of the support plate by a height corresponding to the thickness of the sheet of paper when the sheet of paper passes along the support plate thus causing the rotating shaft to rotate, an amplifying section operatively coupled to the rotating shaft to amplify an amount of rotation of the rotating shaft, and a sensor operatively coupled to the amplifying section for sensing the amount of rotation amplified by the amplifying section, wherein the feeding of two or more overlapping sheets of paper between the pairs of a driving roller and a driven roller is detected.
Also, the apparatus may further comprise a cover plate disposed between the support plate and the rotating shaft in parallel with and spaced apart from the support plate, thus defining the predetermined paper traveling path between the support plate and the cover plate and guiding the sheet of paper passing on the support plate along the predetermined paper traveling path, the cover plate having a plurality of driven roller through-holes which allow parts of lower portions of the driven rollers to pass therethrough so that the outer surfaces of both the driving rollers and the driven rollers contact each other, and a plurality of extending contact arm through-holes which are each disposed between two driven roller through-holes and allow bottom portions of the extending contact arms to pass therethrough so that the bottom portions of the extending projections contact the top surface of the support plate.
The amplifying section preferably includes a pivoting rod fixedly mounted at one end thereof on one end of the rotating shaft and extending perpendicular to the rotating shaft, a connecting shaft fixedly connected to the other end of the pivoting rod and disposed parallel to the rotating shaft, and a link member rotatably connected at one end to the connecting shaft and disposed parallel to the pivoting rod.
Also, the sensor is preferably a magnetic sensor with a rotational center axis is rotatably connected to the other end of the link member.
The length of the end portion of the extending contact arm extending toward the support plate is preferably smaller than that of the pivoting rod.